标题: 大全语法 [打印本页] 作者: rainbowmanutd 时间: 2012-4-9 09:56 标题: 大全语法 1. At a time when it was unusual to do it, Dorothy Sterling wroteabout such major figures of Black history as Harriet Tubman and W. E. B. DuBois. (A) it was unusual to do it (B)it was unusual to do so (C) doing that was unusual (D) that was an unusual thing to be doing（B） (E) it was not usual to do